It's a fascinating experience when the bite inside the mouth (especially cheek) gets cured automatically in short span of time. How is this possible as the mouth is exposed to bacteria and always wet? Search for the reason in web returned results for the remedies for bite inside the mouth. I couldn't find any entry explaining how the heeling happens so fast given that mouth is germ prone area.
One reason the mouth heals quickly because it's very well vascularized (meaning it has a lot of blood vessels). Yes, the mouth does have a lot of bacteria, but so does the rest of you: humans contain 10x more bacterial cells than human cells, and a lot of those bacteria are extremely helpful to have around. Natural bacteria alone will not reduce healing. Infection with "bad bacteria" can reduce healing, but unless a person has poor oral hygiene, there is no reason to suspect they will have "worse bacteria" in their mouth compared to anywhere else on their body. Also, the tissues in the mouth have simple structure, meaning it is easy to rebuild them. For more information you can visit http://www.joseylanedentistry.com/3-reasons-why-your-mouth-heals-faster-than-other-parts-of-your-body/